Second Life is an online virtual world consisting of hundreds of interconnected large-scale areas populated by interactive avatars, whose players may choose to take any form they can create or purchase. The major form of short-distance transportation is flight, while transportation between areas is typically performed through teleportation; both abilities are innate. The "main grid" is restricted to those 18 or over, as some regions contain strong violence or sexual content. A teen version for those 13 to 17 was available until the end of 2010, when it was shut down. Those aged 16 or over were transferred to the main grid, while those 15 or under had their accounts frozen until they reached 16[1].

Second Life is accessed with its client software, also known as a "viewer". The client connects to the Second Life Grid, a cluster of machines running the server software. Third-party clients, most of them based on the (almost) open-source official client, are popular among users.

Second Life has over 8,268,883 registered users and 1,548,131 active users as of July 21, 2007; logged-in users range from 20,000 to 60,000 at any one time. The system is funded through a combination of account subscriptions and "tier" (a form of land value tax). Users have the option to own or rent land parcels in a variety of sizes - as in real life, some owners may zone their land to restrict certain activities, such as commercial development. Business in the world's virtual currency (exchangeable for real-world funds) is encouraged by the Linden Research, and a variety of content vendors have sprung up to meet demand.

Second Life was started in 2003 as a project by "Linden Research, Inc." doing business as "Linden Lab".
Second Life's primary attraction has always been the level of customization; from the ground under your feet to the clouds in the sky. This was quite literal since the world's developers intended for the user to be able to create the world to their desire, as is quoted in the Second Life overview on its site:

"Second Life is a virtual world - a 3D online persistent space totally created and evolved by its users. Within this vast and rapidly expanding place, you can do, create or become just about anything you can imagine. Built-in content creation tools let you make almost anything you can imagine, in real time and in collaboration with others."

Second Life is considered by some to be a variant of the Massive Multiplayer Online Role Playing Game, or MMORPG for short. The true answer to the question "is it such a game?" is "yes and no" - Second Life is technically not a role-playing game by itself.
Also, unlike other role playing games, there is no goal to reach, no levels to gain, no enemies to defeat. Rather, it is a platform that allows games and worlds to be built within its framework, and also allows for members to build economic ventures (with highly-controversial real-world implications). Hence, pegging Second Life (and other environments like it) to a particular definition is very difficult. Other descriptive genres have been devised or adapted to describe Second Life:

Second Life avatars can be customized to the point where they look exactly like one's Fursona.

Upon registering, a player receives a personal avatar to represent them in the virtual world. The appearance of one's avatar is fully customizable and can be shaped and resized almost like clay. Additionally, there are many player-made accessories for one to dress their avatar up with. "Body parts" can also be made, which includes things like anthropomorphic features such as tails, pointy ears, animal heads, paws, etc. Most furries active in Second Life have these kinds of avatars.

Until April 2007, membership on Second Life required a credit card or SMS-capable cellphone, both for security reasons and because each region has its own content rating, from PG to Mature (which can be very mature at times); such prerequisites were dropped by 2007. Also, current members have the option of changing their billing information in the members area so their membership fees can be deducted through PayPal.

On September 8th 2006, Linden Lab reported via a security bulletin (which was also emailed to all SL users) that the servers holding player account information had been attacked using a zero-day exploit. According to Linden Lab, this attack on the servers may have begun as early as September 3rd and they only noticed an increase in activity on the 6th which they then quickly locked out. Their investigation showed that the attack allowed a significant amount of customer account information to be downloaded such as credit card numbers, PayPal transaction ID's, real life names, Second Life names, account passwords, and contact information.

As part of their effort to improve the security of their servers, Linden Lab had invalidated the passwords (assuming they were already compromised) of all Second Life users and has required said users to reset their passwords. Linden Lab further mentioned that while the compromised payment information was encrypted, no encryption is unbreakable given enough time and computing power. They had thus stated that if any SL user believed themselves to be the victim of credit card fraud, they (the user) should contact their credit card company.

The furry fandom has a major presence in Second Life, with multiple areas devoted to providing accommodation, entertainment and creative services specifically for members of the furry community. Themes range from the pedestrian to the bizarre, although trees are common in furry haunts. Each user can create their own objects from the inbuilt primitives, but the majority of users rely in part on objects created and sold by others. These include body parts for avatars, accessories, vehicles (which may be purely aesthetic or provide extra functionality), toys, pose balls for avatar animation, and scripts to provide extra features (like "push" and "shield" defensive/offensive capabilities).

Second Life has become one of the popular forms of online entertainment for members of the furry fandom; at last count there were over 500 furries registered as Second Life users, and the true number is probably several times that by now. This arose out of the fact that the avatars, humanoid objects representing the user, are very customizable and the world's disposition for allowing users to create anything has made the concept of a virtual "fursuit" possible. Many furries of Second Life don't like to be considered to be wearing fursuits. Instead, they pretend it is their real body. These consist of a variety body parts which are attached to the user's avatar. These parts include tails, wings, legs, and so on - some have even made complete sets that resemble mythical beasts such as dragons, complete with scripted flame effects. Such avatar add-ons can be sold by their creators, who retain the ability to control distribution of their objects as part of their copyright, enforced by inbuilt copy restrictions. Some choose to give works away for free, for apparently altruistic or promotional purposes.

The high interactivity is also a plus for online social networks - as a result, various furry communities began to pop up in the world and are now a sizable force in the virtual world. In the October 2005 issue of Computer Games, "Furries" (used as a proper noun) were noted as a major user-base in Second Life in an article about the use of MMOs for self-actualization.[2]

In (early 2006?), a "furry admin" meeting for all furry and/or furry-friendly sims' administrators or owners was held to discuss several unifying strategies regarding the fandom population in world (Inferniel Solvang was the lead fur for this particular encounter.) Of the many proposals, one was the creation of a common, official symbol or logo for identifying purposes for sim or fur.

The final design, a SL logo inspired image, came to be thanks to the design of SL furry artist, Yiffy Yaffle. The logo can be viewed on most of the older furry sims, with propagation to newer ones going at a slow, but steady rate.

Members can purchase whole regions (256m × 256m block of land) called Islands from Linden Lab, effectively renting a whole processor for the region. Many such regions are home to furry communities.

Prior to the creation of islands, every region belonged to a large land mass (sometimes called Mainland). Parts of these regions sometimes ended up dedicated to specific groups, including the furry fandom.

Second Life Promotional Video -- This file is directly available on the Second Life Home page. The video is linked to an image titled "watch the video" that will alternate with the free trial promotional image link. There is also a Quicktime version of the video.